The   United States of America   is a   federal republic [1]   consisting of 50   states , a   federal district   ( Washington, D.C. , the   capital city   of the United States), five major   territories , and various   minor islands . [2] [3]   Both the states and the United States as a whole are each sovereign jurisdictions. [4]   The   Tenth Amendment to the United States Constitution   allows states to exercise all powers of government not delegated to the federal government. Each state has its own   constitution   and government, and all states and their residents are represented in the federal   Congress , a   bicameral   legislature consisting of the   Senate   and the   House of Representatives . Each state is represented by two senators, while representatives are   distributed   among the states in proportion to the most recent   constitutiona...